This project has been, and continues to be, concerned with the mechanisms of binaural hearing, especially those involved in detection and lateralization of complex sounds. Recently, the primary interest has been with the processing of high-frequency waveforms. The experimental results indicate that the so-called duplex theory of sound localization is appropriate only for pure tones; for complex waveforms the binaural system is capable of utilizing interaural time differences at high frequencies almost as well as at low frequencies.